Polychlorinated biphenyls (hereinafter referred to as PCBs for brevity) have been used in many applications for more than forty years. PCB-filled transformers have found wide use because PCB does not burn or sustain fire under conditions of internal arcing. PCB-filled power and industrial capacitors are significantly smaller, more reliable, more durable, and safer than oil-filled capacitors. In short, PCBs are ideal fluids for electrical equipment and heat-transfer systems because of their heat stability, nonflammable nature, low volatility and good viscosity characteristics at operating temperatures.
However, evidence has recently been presented which shows that PCBs are widely dispersed in the environment and have the potential to damage both the environment and people. Studies have shown that adverse health effects such as liver damage and chloracne may result from inhalation or skin absorption of certain types of PCB compounds. Also, PCBs have recently been classified as suspect teratogens, which means that fertile females should avoid exposure to these compounds.
The manufacture of PCBs has currently been discontinued and Environmental Protection Agency regulations have been issued under the authority of the Toxic Substances Control Act to control the materials now in use in the United States. These regulations, which became effective July 1, 1980, define any material containing 50 ppm or more of a mono- or polychlorinated biphenyl as a PCB and regulate its use and disposition. Currently, the only permissible disposal of a PCB is by incineration in an EPA-approved incinerator (none exist) or by burial in an EPA-approved landfill.
Either disposal method requires transportation from the point of use to the disposal site, thereby increasing the chances of inadvertent release into the environment. Furthermore, the siting of incinerators to burn PCBs has met strong opposition from local residents of areas under consideration. Consequently, an economical process which facilitates disposal of oil contaminated with PCBs is a most sought-after solution.
At the Paducah Gaseous Diffusion Plant, operated by Union Carbide Corporation for the U.S. Department of Energy, a large lubrication oil system was found to be contaminated with 67 .mu.g of Arochlor 1254 (a Monsanto Chemical Corporation formulation) per gram of oil. Since this level of contamination was above the 50 .mu.g/g PCB level set by EPA and since serious operational problems as well as significant economic losses would be sustained if the contaminated units were to be taken off stream, several methods were attempted to effect the removal of these PCBs.
Fuller's earth, normally used to remove oxidation products from lubrication oil, reduced the PCB content by approximately 20 percent after slurrying a 10 percent volume of this material with the oil for 18 hours. Similar tests and results were obtained with activated charcoal. Although these tests resulted in a reduction of the PCB content of the oil, it was not a satisfactory solution since significant disposal problems were encountered with the use of adsorbents.
An evaluation was also made of the use of organo-sodium compounds such as sodium biphenyl and sodium napthalene for PCB removal. It was necessary to use a quantity of these compounds greatly in excess of the theoretical amount required to reduce the PCB to an acceptable level. Both the material cost and the potential alteration of lube oil quality precluded the use of this method. In addition, experiments were carried out using combinations of adsorbents along with organo-sodium compounds to effectuate PCB removal with fair results. However, none of these efforts approached the effectiveness of the subject invention.